1. Field of the Invention
The present invention relates to a display technical field, more particularly, relates to a method for producing a low temperature polycrystalline silicon thin film, a thin film transistor and a method for producing the thin film transistor, an array substrate, and a display apparatus.
2. Description of the Related Art
With a rapid development of a technology of flat-panel display, an Active Matrix Organic Light Emitting Diode (AMOLED) is going to be popular because it has many advantages, such as lightweight, thin thickness, self-luminousness, high response speed, etc. The AMOLED comprises an active switch, an insulation layer, a transparent electrode, a luminous layer and a metallic layer formed on a substrate in this order. The active switch is connected to the transparent electrode through a via to control writing of an image data. Currently, with the AMOLED becomes larger and larger in size, a Low Temperature Poly-silicon (polycrystalline silicon) Thin Film Transistor (LTPS-TFT) is often used as a pixel switch control element in the active switch. Accordingly, the quality of a low temperature polycrystalline silicon thin film for the LTPS-TFT has a direct influence on the electrical performance of the LTPS-TFT. As a result, there is an urgent need to improve the technology of producing the low temperature polycrystalline silicon thin film.
In prior arts, the method for producing the polycrystalline silicon thin film in a back panel of the AMOLED mainly comprises Excimer Laser Annealing (ELA), Solid Phase Crystallization (SPC), Metal-Induced Crystallization (MIC), and so on. However, so far, only the ELA is adapted to produce the polycrystalline silicon thin film of an active layer of TFT in the back panel in a large scale. FIG. 1 shows a process of producing the low temperature polycrystalline silicon thin film by the conventional ELA. As shown in FIG. 1, firstly, forming a buffer layer 103 and an amorphous silicon layer 104 on a glass substrate 101 in order, then performing a laser annealing on the amorphous silicon layer 104 with a laser beam 105, and then a polycrystalline silicon thin film having a thickness of 0.3 μm˜0.5 μm may be resulted.
In the research of the ELA, researchers are all trying to develop a low temperature polycrystalline silicon having a large grain size so as to obtain a low temperature polycrystalline silicon thin film transistor with a high mobility. Unfortunately, so far, the researchers do not find a proper method to obtain the low temperature polycrystalline silicon having the large grain size yet, although the quality of the low temperature polycrystalline silicon thin film is related to many factors, such as, an output wavelength, a pulse width, an energy distribution and uniformity, an energy density and a pulse frequency of an Excimer Laser; a production method, a thickness, a dehydrogenation method and an annealing atmosphere of an original amorphous silicon film, etc.